All apps losing and regaining focus every 10 seconds when UE4 is running


I’ve recently had some problems with UE4. When I have the engine on, every 10 seconds or so, the app I’m currently using is losing its focus, just to regain it after a second. It’s really annoying, because it interrupts my activities, causes drop-down menus to hide etc. Any idea what might be causing this?

I use Windows 10 x64.

Verifying the engine files, creating a new project and turning off Perforce helped. Probably it was caused by Perforce…